Bulletin d’avalanche

Galena Summit & Eastern Mtns

Sawtooth Avalanche Center
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Danger d’avalanche

Sun
Alpin
4 · Fort
Limite forestière
3 · Marqué
Sous la limite
3 · Marqué
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Périmé — ce bulletin a expiré 3 years ago. Vous consultez des conditions passées, pas le bulletin en cours.

Points saillants

Very dangerous avalanche conditions exist. Multiple large avalanches were remotely triggered in this zone yesterday and you can easily trigger similar slides on many slopes today. Avoid traveling on or underneath slopes steep enough to avalanche. Slides can be triggered from long distances away from steeper slopes and can run into gentler terrain below.

Problèmes avalancheux

  • Persistent Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Likely
    Taille
    2–3

    Recent storms brought 1+ feet of snow to upper elevations in this zone. Multiple large remotely-triggered avalanches occurred above the East Fork of the Big Wood River yesterday (photo at right/above). These slides failed on a uniquely widespread and fragile layer of snow that developed during the December drought. Dig down and you'll find facets and/or surface hoar on shadier aspects and crust + facet combinations on sunnier slopes. A dense, 2-3 foot thick slab of snow is uncomfortably balanced on top of these layers.

    Triggering similar slides is likely again today. You can trigger avalanches that fail on these weak layers from long distances away from steeper slopes. Some of the triggered slides from yesterday released over 1,000' away from where the slope initially collapsed.

    The recent snow is adding significant stress to the persistent weak layers in the snowpack, and represents the first major loading event that large portions of this zone have experienced. Yesterday's triggered slides clearly indicate that the snowpack is not reacting well to this loading. At lower elevations, you'll find a rain-soaked snowpack. Here, you can trigger slabs that have a wet character as the day warms up and brief pockets of sun melt the new snow.  

    This large remotely-triggered persistent slab avalanche on a NE slope at 9400' above the East Fork of the Big Wood broke 250ft wide and ran over 1000' downslope.

  • Storm Slabs

    • Alpin
    • Limite forestière
    • Sous la limite forestière
    Probabilité
    Very Likely
    Taille
    1–2

    The ongoing storm brought 1+ feet of snow to upper elevations and up to an inch of rain to lower elevations. Expect to find a range of problems involving this new precipitation. At upper elevations, you'll find reactive wind slabs large enough to bury you and you may be able to trigger loose snow avalanches that run fast and far on crusts. At lower elevations, the snowpack is still saturated from recent rains. As the day warms, be on the lookout for wet snow problems like loose snow avalanches that gouge deeply through a saturated snowpack. At middle elevations, you'll find a range of dry and wet snow problems. 

    Enough recent snow has fallen that these slides will easily be large enough to bury you. Importantly, natural and triggered slides involving the new snow can trigger the much larger, more destructive persistent slabs described above. 

Avalanche Discussion

We head into the weekend with a very dangerous snowpack in our mountains. Here's a quick rundown: Uniqely widespread and fragile weak layers are resting under dense 2-3 foot thick slabs. Three hot, bright days started out the week, with temperatures rocketing into the mid 40s F in the mountains. A wet loose and wet slab avalanche cycle ensued. Thick crusts formed on solar aspects, with thinner, more fragile crusts on the solar margins (E/SE and W aspects). On shaded slopes you can find rain/rime/drizzle crusts that extend up to at least 10,000' underneath the new snow. Beginning Thursday, a warm, wet storm took aim at our area and delivered significant amounts of water to the mountains and valleys. The snowpack did not react kindly to this.

Yesterday, as I walked along a ridge above the East Fork of the Big Wood, I remotely triggered at least 4 large avalanches that failed on the prominent weak layer in the snowpack. One of these slides was triggered from over 1,000 feet away. All of these would have easily buried you, and some would have done much worse. These are exactly the types of slides that you can trigger today. Smaller slides involving the new snow will also be easy to trigger. Triggered slides can break down into he weak layer underneath, producing much larger, more dangerous avalanches. 

The pull of the fresh snow can be hard to ignore. I get it, I'm a hungry dog for powder just like you are. But you'll need to keep your focus on the hazards posed by the mountains in order to stay safe today. Avalanches can fail in places you've never seen them before, and can be triggered from the run-out zones beneath steeper slopes. Head into the mountains today with open eyes and a conservative travel plan, and work with your partners to stick to it. I'd love for everyone reading this to find a way to splash some powder across the smiles on your faces. But my biggest wish for you is to come home safe at the end of the day today, with good stories to tell, ready to go do it all again tomorrow. 

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